1. Field of the Invention
The present invention relates to a seat recliner assembly having a base plate which is to be secured to the lateral side of a seat cushion, an arm to be secured to the lateral side of a seat back and which is pivotably installed at the lower end thereof to the base plate, and an engagement mechanism provided on the arm and base plate and which adjusts the pivoting of the arm, thereby permitting to adjust the tilt angle of the seat back.
2. Description of the Prior Art
Many various seat recliner assemblies have been proposed heretofore. One of the prior-art seat recliner assemblies is constructed as typically shown in FIGS. 8 and 9; the assembly has a base plate 2 to be secured to the lateral side of a seat cushion 1 and an arm 4 to be secured to the lateral side of a seat back 3, the arm being pivotably mounted at the lower end thereof on the base plate 2 and having upper teeth 100 formed at the lower end thereof, the base plate 2 having pivotably installed thereon a toothed member 101 having formed therein lower teeth 102 is engaged with the upper teeth 100, whereby the upper and lower teeth 100 and 102 are put into and out of engagement between them by moving a release lever 103 vertically. The lower end of the arm 4 and the upper edge of the member 101 are toothed as machined by cutting or pressing. The upper and lower teeth 101 and 102 are engaged with each other or disengaged from each other to adjust the tilt angle of the seat back. The engagement teeth had to be sufficiently rigid since the load applied on the seat back 3 concentrates to the engaged teeth. Therefore, the toothed member 101 and arm 4 had to be made of a rather thick steel plate and also the upper teeth 100 at the lower end of the arm 4 and the lower teeth 102 at the upper edge of the member 101 had to have the same thickness of the arm 4 and toothed member 101.
In the prior-art seat recliner assemblies in which the upper teeth 100 and lower teeth 102 are formed in the arm 4 and member 101, respectively, which have to be sufficiently thick, the weight of the arm 4 and toothed member 101 is rather great. If any misalignment exists in the direction of thickness between the upper and lower teeth 100 and 102, these teeth will not possibly be well engaged. To prevent such misaligned engagement between the teeth 100 and 102, they are formed as thick as possible to ensure any, even partially, positive engagement, which is adopted in some of the prior-art seat recliner assemblies that have been proposed. Along with the increased thickness of the teeth 100 and 102, however, the arm 4 and toothed member 101 have to be thick correspondingly, which results in the increased weight of such assemblies.
Also in the prior-art recliner assemblies, when the toothed member 101 is pivoted, the lower teeth 102 and the upper teeth 100 interfere with each other. So the prior-art such assemblies are diadvantageous in that the interfering portions are abraded or broken and that the reclining operation cannot be smoothly done. Especially it cannot be expected that the toothed member 101 can be pivoted positively.